Milling apparatus



Filed June 27, 1955 2 Sheetsf-Sheet l n Ei f 3% .fm n. i ffw V l V/ n4.a ew wf. f m il 7 u s f .ww MM/ WW am www am Mmfmm/ 3 W 4 M/aw mwa 5 4M, f IJW. 4 L 5 MM .p 8 W 0 /6 M 3 ....wlf

7' TOR/VE Y Sept. 6, 1.960

M. D. lssr-:RLIS v 2,951,648

MILLING APPARATUS Filed June 27, 1955 2 Sheets-Sheet 2 A. INVENTOR.

' MORRIS Q [55.55515 SMQ@ United States Patentl MILLING APPARATUS MorrisD. Isserlis, 117 Riverview Ave., Highland Park, N J.

Filed June 27, 1955, ser. No. 518,138

8 claims. (ci. 241-55) application SerialA No; 503,915 ledt April l 26;`19,55, now

abandoned.

-Inone knowntype of milling machine, high velocity;

Z force generated bythe rotating air mass; classification is achieved.

If desired, the above-described machine may be enrployed as a hammermill which provides particle classi* iication by making. the impellerblades of suiiicient length that-they can. make direct physical contactwith the mate'- rial to be pulverized.

Milling -apparatus embodying the principles of the in'- ventionmay alsoinclude inlet and outlet pipes at the center of the housing and axiallyaligned. In this constructipnof a milling machine, the impeller whichhas its blades lyingY in planes which extend radially from the axis onwhich the inlet and outlet are aligned,A is. provided with afsolid disksecured to the impeller 'approxi-v mately midway between. the inlet andoutlet and. orie` ented in a pl-ane transverse to the oniwhich the Thus,efficient inlet and outlet pipes are oriented` Thus,` in effect,

jetsof 'afiiuid are employed to'pulverize `solid-materials t to a nestate. IIn order to achieve the requiredtfluid velocity, t extremelyhigh` fluid pressuresrnust be provided andcornparatively complex andexpens-ive auxiliary apparatus is required for this purpose. The cost ofsuch auxiliary apparatus is prohibitive. In addition, otherknownitypesof milling apparatus dolnot readily provide milling 4to iineparticle size and, concurrently, iine particle size classification.

Accordingly, the principles andobjects-of this invention. are-v directedto providing milling 'apparatus of new and novel form `capable ofpulverizing solid` materials to. substantially any desired particle sizeand, at the same time, providing useful classification in the fineparticle range. The objects of thetinvention are also concerned withproviding an improved milling apparatus which is comparativelyinexpensive whilev being comparatively simple and rugged inconstruction.

` III general, `the principles and objects ofV this-invention areaccomplished by the provisionof milling apparatus including a stationaryhousing having aslarge volume at` the center thereof `and tapering to aminimum volume` ab the periphery thereof.A Thus, the housing maycomprise a pairof generally conical members or sections off spheresorwthe `like coupled together attheir bases.A

An impeller is provided at the center of thehousing andA l iiavingcomparatively shortA blades sothatthe diameterof-theimpelleris smallerthan the diameterl ofthe housing-, along its long axis.` Means areprovidedu `for intro`` ducingmaterial. to be` pulverized at theperiphery. of.` the liousingand `for withdrawing` the pulverized`particles at thercenter of the housing..

t In order to` achieve the desired pulverizing.operation;- the impelleris rotated -at high speedv whereby. the large volume of air at thecenterof the housingfis rotated the direct flow path between the inlet andoutlet pipes is-'bl-ockedy by the soliddisk and the material introducedinto the. housing is forced to the periphery and cannot reach theoutletl before it has been pulverized. In this way, the classifyingaction of the apparatus is improved.

The. invention is described in greater detail by refer,encetoithedrawing wherein:

Fig. 1V is a sectional elevational view of milling apparatus embodyingthe principles of the invention andV al schematic:` representation ofauxiliary apparatus employed therewith;

Fig. 2` is atsectional view-along the line 2--2 in Fig. 1; Fig. 3 isasectional elevational view of a por-tionof; another embodiment oftheinvention;

Fig.w4 -is a sectional elevational View of still another embodiment ofythe invention and auxiliary apparatusemployed therewith; and Fig.5 is` aperspective View of the impeller employed with the apparatus of Fig: 4f

Referring to the drawing `and particularly to-Figs. 1 and 2,`milling-.apparatus embodying the principles of the invention: includesa housing 12 comprising a pair oft similar dished members 14 and 16 inthe form of cones orsections of spheres or the like. Thedished membersare Vshown as sections of spheres. 'The/(lished` member 14ihas an apexor center 18 and ar-im 20 and the dishedV member- 16 has an apex orcenter 22 and a rim 241. Thedishedlmembers are secured together at theirrimsw by means of bolts 26 or the like with a gasket- 2S of rubber orthe 'like interposed between the rims. The dished. members, thus, arewidely spaced at their centers offaplices and theA spacingbetween themdecreases-to a minimum: at. the region of `contact'` between the rims 20and 24'.A Thus, `as one. important feature of` the invenfA t tionsztlie.housing 12 -encornpassesV a` large volume atits and'- energy istransferredthroughout the volume of.

tlie housing to the periphery thereof where a small volume of` air isrotated at high speed. The frictional forces generatedV by they rapidlym'ovingnair mass,.par tcularlyatthe periphery of the liousingadjacent-tothe wall thereof, create extreme` turbulence and eddy. currents. Thus,the solid material introduced into the hous-` ing at the periphery isretainedatthe periphery due to centrifugal -force and the eddy `currentscause-violent collisions of the particles so that they pulverize eachother due to self-impact; A suction force applied at the outlet. from"the. housing at the center thereof draws the iine particles out of thehousing with the size of tlie par-t ticles` removed being determined bythe resultant of the4 flow of airlin-to the. housing througlitleinlet'andout of housing through the outlet andhof` the.centrifuga.l 5,

center'between the apices of thew dished: members and: the volume`decreases to a minimum at the.- periphery ther'eof; The dished membersmay be of cast iron, steel` onthelike. t

A shaft 3'0 is suitably rotatably jo-urnaliedinthevwall ofthe dishedmember 14 and aligned with the' centers 18-and221'of the dished members14 and 16, respectively.'` The. shaft extends Iinto the interiorr ofthe`housing` 12. `Within` theV housing, the shaft 3i]` carries anirnpeller32' including a plurality of varies or blades` 34p which lie in planeswhich extend radially from the shaft 30 as `shownin Fig. 2. Outside thehousing, theshaft 305 is coupled to a suitable motor drive apparatus 364which may. comprise a motor yal-'one or a motor `and belt` couplinglarrangement or the like.

The impeller blades 34, have edges 38 and 40 which, prefrably,.followthe contour of the in'ner walls of the housing and extend closelyadjacent to said walls. Thus, the width W of the blades is` as large `aspossible. to. provide maximum`` impeller capacity. The length 112.

of the impeller blades is such that the diameter of the impeller issmaller than the diameter of the housing at the rims of the dishedmembers by such an amount that theimpeller blades donot contact thematerial which is pulverized at the periphery of the housing. Afavorable ratio Vof housing diameter to impeller diameter is of theorder of two to one.V

With the housing vertically disposed as shown in Fig. 1, an inlet pipe42 is coupled to the periphery of the housing at the bot-tom thereof andsecured to the wall of one of the dished members, for example the dishedmember 16. The pipe 42 may be disposed at substantially any desiredangle with respect to the housing and is open to the atmosphere to allowair to enter with the charge of material to be pulverized. A hopper 43which carries the material to be fed into the housing is coupled by apipe 44 to the inlet pipe 42. The pipe 44vmay contain apparatus forfeeding material such as ascreW conveyor or the like. Y

The dished member -16 is provided with an outlet opening 46 at the apexthereof which comprises an outlet for the pulverized material. Thus, theoutlet of the milling apparatus is positioned at the center of thehousing l2. An outlet pipe 48 is coupled directly to the outlet opening46 and a screw conveyor driven by a motor 52 is disposed within the pipe48. A conventional material separator 54 which separates the ai1 and thepulverized particles which fall into the screw conveyor 50 is coupled tothe outlet pipe 48, preferably, immediately adjacent to the outletopening 46 in the housing 12 and a suction fan 56 is suitably coupled tothe dust collector through an lair line 55 controlled by a damper 57. Arotary valve 58, driven by the motor 52 and adapted to withdrawpulverized particles without disturbing the air ilow in the outlet line,is coupled to the outlet pipe 48 and pulverized material is collectedtherefrom.

In operation of the milling apparatus 10, the impeller 32 is first setinto rotation at high speed, for example at about 20,000 feet per minutetop speed. Thus, the air within the housing is set into rotation andlarge centrifugal forces lare generated therein. Then, the suction fan56 is turned on an-d the feeding of solid materials 'and air (or steamor the like) from the source 44 is begun. As the solid materials are fedinto the housing, they are swept to the periphery thereof Where they arepulverized due to self-impact. The theory of operation is that theimpeller sets the large mass of air at the center of the housing intorotation at high speed and the rotational energy thus developed istransferred throughout the volume of the housing to the peripherythereof. At the periphery of the housing, the rapidly moving airgenerates large frictional forces which create extreme turbulence andeddy currents and the solid materials swirled about in these eddycurrents are pulverized due to self-impact.

As the solid material is pulverized, the resulting particles which 'areof many dilferent sizes tend to become classified according to sizealong the diameter of the housing with the iinest particles orientedtoward the center of the housing in the vicinity of the outlet pipe 48and the larger particles retained near the periphery due to thecentrifugal force of the rot-ating air. The particles thus classiedwhich are too large to leave the housing also fact as a grinding mediumon the incoming material. The ground particles are withdrawn from thehousing 12 by the air flowing through the housing from the inlet pipe 42and out of the outlet opening 46. The suction force `applied to thesystem by the suction fan 5.6 under the control of the damper 57determines the air flow through the system and through the housing andthe resultant force of this air ilow and the centrifugal force of themass of rotating air determines the size of the particles Vwithdrawnfrom the housing. If very fine Vparticles are desired, the suction forceis made small and the grinding time is thus made comparatively long andif larger particles are desired, the suction force is increased and thegrinding time is thereby reduced.

In operation of the milling yapparatus 10, the impeller 32 may berotated in a counterclockwise direction as viewed in Fig. 2 such thatthe flow of air rotated thereby is opposed to the flow of solid materialand air entering the housing through the inlet pipe 42. This arrangementprovides increased turbulence at the point of entry of solid materialand promotes the attrition thereof. yIn addition, if the feeding ofsolid material into the housing is discontinued, the counterclockwiserotation of the air within the housing may be employed to clean out thehousing by driving the contents thereof out through the inlet pipe.Alternatively, the rotation of the impeller may be in a clockwisedirection and in the same direction, substantially, as the ow of air andsolid materials into the housing through the inlet v pipe.

, As described above, the classification of the milling Iapparatus 110depends on the centrifugal force within the housing and the ow of airtherethrough. In addition, classification is effected by the reductionin velocity of the air which enters Ithe housing at comparatively smallvolume and expands at the center of the housing to a larger volume.

Effective pulverizing is promoted in the milling apparatus of theinvention by the considerable energy input to the system in the largemass of air rotated at high speed at the center of the housing. Inaddition, since the grinding action is performed by particles of solidmaterial colliding with each other and not with portions of theapparatus, there is substantially no wear on the component partsthereof. The apparatus described herein may be employed to pulverizemany different types of materials, for example, pigments, abrasivedusts, ceramics, waxy materials and the like. Y

Another embodiment of the invention shown in Fig. 3 employs all of thefeatures of the apparatus shown in Fig. l except that an impeller 60 isemployed which h-as blades 62 which extend close to the periphery of thehousing. Thus, the material to be pulverized which is retained at theperiphery by centrifugal force is pulverized by direct impact with theblades 62 of the impeller and the ow of air through the housing asdescribed above provides classiiication and removal of the particles ofthe desired size. The tips of the blades comprise, or yare coated with,a wear-resistant material such as Stellite which is an alloy of cobalt,chromium, tungsten, carbon, and silicon.

Referring to Fig. 4, a modification of the invention includes a housing70 of the general form described above and comprising a dished member 72having an opening 74 at its center and a dished member 76 having anopening 78 at its center. The dished members 72 and 76 are securedtogether at their peripheries with their concavities opposed and withthe center openings 74 and 78 aligned. Thus, the dished members arewidely spaced at their centers and the spacing between them decreasestoward the periphery of the housing.

A shaft 80 having one end connected to a motor extends through theopening 74 in the dished member 72 into the `housing interior. The shaft80 is in axial alignment with the two center openings 74 and 78. Theshaft 80 has a smaller diameter than the opening 72 and is suitablysupported, for example in bearing blocks 84, positioned outside thehousing 70 suitably supporting themselves in any convenient manner. Aprotective sleeve or the like (not shown) may be provided over the shaftin the vicinity of the opening 74. Within the housing, the shaft carriesan impeller 86 of the general type described above. The impellerincludesV a plurality of'blades 88, for example four blades, which, ineffeet, lie in planes Vsubstantially perpendicular to the shaft 80.AEdges 90 and 92 of the-impeller blades followrtliefcontour ofthehousing alongtheir length. The impeller. blades arepreferablysubstantially as wide as the, distance..` between the wallsof thehousing along their entirelength so that only the minimum clearanceispresentbet'ween the edges of the ,blades and the walls ofthehousing.The clos'e spacingofthe blades tothe housing walls is designed topromote the building up of pressurebetween the blade. edge and the wallso that pulyerized material is substantially prevented from flowing-`therebetween. lThe impeller blades-may be of any desired lengthdepending Ion whether or not it is desired to make direct contactwiththe; material being pulverized. f

According-to the invention, a.metallic disk or plate 94 is` secured. tothe impeller. The disk` is disposed substantially midway between the'edges 90 and 92 of the impeller blades v$8 and along the long axis ofthe housing substantially perpendicular to the shaft 80. The diskdiameter is not critical and may be equal to, slightly smaller than, orslightly larger than the diameter of the impeller. Thus, the disk, ineffect, blocks the direct iiow path between the central openings 74 and78 in tzhe dished members 72 and 76. Disk 94 is seen in In addition, inthis embodiment of the invention, material is to be pulverized is fedinto the housing at the center thereof and through the central opening74 in the member 72. To this end a lpipe 96 is secured to the opening 74surrounding the shaft 80 and is coupled to a hopper 98 or some othersuitable reservoir of material to be fed to the housing to bepulverized. The outlet system employed with the 'apparatus shown in Fig.4 may be the same as that shown in the apparatus of Fig. l

. with the outlet pipe 48 coupled to the central opening 78 in thedished member 76.

One advantage of the apparatus shown in Fig. 4 derives from the factthat the material inlet is at the center of the housing where there issubstantially no pressure and substantially no energy is expended infeeding material into the housing. Another advantage arises from thepresence of the disk 94 on the impeller which promotes the classifyingaction of the apparatus. Classification is improved because whenmaterial is fed into the housing even the finest particles thereincannot flow directly into the outlet pipe 48 due to .the presence of thedisk. Thus, as the material is fed in, some of it strikes the disk as itflows to the periphery of the housing due to the centrifugal forcegenerated by the impeller. During the movement to the periphery of thehousing, the material is struck by the blades 'and pulverizing isbeg-un. When the material is properly pulver-ized and it is drawn out ofthe housing by the applied suction force and by the ow of airtherethrough, it passes upwardly between the impeller blades whichstrike the material and provide an additional pulverizing action. Theoutgoing material is directed through the blades and is prevented frompassing between the edges of the blades and the wall of the housing dueto pressure generated in that area by the rotating impeller.

What is claimed is:

1. Milling apparatus which operates by means of air turbulencecomprising a stationary housing consisting of two walls Widely spaced attheir centers and becoming gradually more closely spaced up to theirperipheries Where they are secured together, an impeller shaft at thecenter of said housing and extending between said walls, and a pluralityof impeller blades secured to said shaft, said impeller blades beingadapted to be rotated at highv speed so that material being milled isretained at the periphery of said housing in la region of considerableair turbulence in which the material in elfect mills itself, said bladeshaving a width substantially equal to the width of said housing, theedges of said blades adjacent to said walls following the contour ofsaid walls, the length of said blades being smaller than the radius ofsaid housing so,thatsaidblades are remotefromme periphery of` the.

housing ,where materialA is milled and'said blades are substalntially,outof. direct contactwith the material` being mi led.

2. Milling appanatus comprising. a, stationary housing consistingoftwo,` generally concavemembers positioned with their centers alignedand widely spaced at their. centers and in contact with each other attheir peripheries, an impeller shaftat thecenter. of said housing,impeller blades secured to said shaft, said blades being substantiallyas wide as saidfhousing and ,having theiredges following the contour ofthe walls of said housing', the length of saidblades being smaller thanthe radiusof said housing so that `saidrblades are remote from theperiphery ofi the housingzwhereimateri-alis milled and saidbladesaresubstantially` -out fdirect' contact with the material? being milled,and a'disk secured'atA its center to said'sliaft' and lying in a planeperpendicular to said shaft substantially midway between the centers ofsaid walls.

3. The apparatus defined in claim 2 and including a inlet opening at thecenter of one of said walls and an outlet opening at the center of theother of said walls.

4. Milling apparatus which operates by means of air turbulencecomprising a stationary housing consisting of two generally dish-shapedmembers oriented with concave surfaces facing each other and havingtheir peripheries secured together, an impeller within said housinghaving an impeller shaft oriented transversely between the centers ofsaid dish-shaped members, said impeller having at least two sets ofimpeller blades, and a disk secured to said impeller shaft and lying ina plane perpendicular to said shaft, said disk having a diametersubstantially equal to the diameter of said impeller, the diameter ofsaid impeller being of the order of half the diameter of said housing sothat said blades are remote from the periphery of the housing wherematerial is milled and said yblades are substantially out of directcontact with the material being milled.

5., Milling apparatus comprising a stationary housing consisting of twogenerally spherical wall members positioned with their concave surfacesfacing each other and with their peripheries secured together, animpeller within said housing and having an impeller shaft orientedtransversely between the centers of said walls, the ratio of thediameter of said housing to the diameter of said impeller being of theorder of two to one, and a solid disk secured to said impeller shaft andoriented in a plane perpendicular to said impeller shaft, the plane inwhich said disk lies being approximately midway between the edges ofsaid impeller blades.

6. Milling apparatus which operates by means of air turbulencecomprising a stationary housing consisting of a pair of walls havingcenters and spaced apart with their centers aligned, material inletmeans at the center of one wall and material outlet means at the centerof the other wall, an impeller shaft at the center of said housing,impeller blades secured to said shaft, said blades being substantiallyas wide as said housing and having their edges following the contour ofthe walls of saidhousing, the length of said blades being smaller thanthe radius of said housing, so that the tips of the blades are remotefrom the material being ground at the periphery of the housing, and -adisk secured at its center to said shaft and lying in a planeperpendicular to said shaft and substantially midway between the centersof said walls, said impeller blades being adapted for rotation at highspeeds to cause air turbulence at the periphery of said housing.

7. The apparatus defined in claim 6 and including a suction fan coupledto said material outlet means for selectively withdrawing groundmaterial from said housing, the speed of said fan being variable toprovide a classifying action on the material withdrawn.

8. Milling apparatus comprising a stationary housing consisting of .twogenerally spherical wall members positioned with their concave surfacesfacing each other and with their peripheries secured together, animpeller within said housing and having an impe11er shaftorientedtransversely between the centers of said walls, the natio of thediametenof said housingto the diameter of said impeller being of theorder of two to one, and a solid disk secured to said impeller shaftandoriented in a plane perpendicular to said impeiler shaft.

References Cited in the le of this patent UNITED STATES PATENTS 427,228Finney May 6, 1890 617,345 Mitchell Jan. 10, 1899 669,897 Day Mar. 12,1901 1,656,862 Loy Jan. 17, 1928 A1,753,936 Moore Apr. 8, 1930

